Posted
by
samzenpus
on Sunday March 04, 2012 @04:44PM
from the skin-of-your-teeth dept.

The Bad Astronomer writes "News is starting to spread about a small 45-meter-wide asteroid called 2012 DA14 that will make a close pass to Earth on February 15, 2013. However, some of these articles are claiming it has 'a good chance' of impacting the Earth. This is simply incorrect; the odds of an impact next year are essentially zero. Farther in the future the odds are unclear; another near pass may occur in 2020, but right now the uncertainties in the asteroid's orbit are too large to know much about that. More observations of DA14 are being made, and we should have better information about future encounters soon."

If it does hit, maybe it will convince those with the cash that asteroid defense is a worthwhile expense.

But it isn't. The chance of anything important being hit is almost nil, while defending from asteroids is extremely expensive. It just isn't cost-effective.

Just look at our wars on "Terror" and "Drugs". Do you honestly think cost effectiveness is ever considered?

Now defending from asteroids won't be politically feasible until we actually get hit by one - when people can actually see it and experience the impact, death and destruction. Some millions of years old crater in a desert is nothing.

Trouble is, a single rocket with a single nuke isn't likely enough to fix a civilization-destroying rock.

Also, given the choice between practically any expenditure and world civilization, of course it's worthwhile. But by the time we get that choice, it's too late to do anything. At the moment, it's something like "building and maintaining a rocket with a nuke" for "1 in a million annual risk to global civilization".-- you can't just say that such a rock is eventually inevitable, because asteroid defense isn't something you buy once and put on the shelf in addition to the upkeep and periodic replacement of weapons, there's the cost of a concerted monitoring program to detect a threat early enough and with an accurate enough orbital solution that the gentle tap of a nuke will eliminate the risk.

It's not easy to come up with actual numbers, but once you factor in the possibility (IMO likelihood) that civilization may well end long before such an impact, it would not be entirely surprising to find that it's actually economically saner to hope for the best than to make preparations.

(It's analogous to a civilian in low-crime areas considering the purchasing and wearing Type III body armor -- the cost, discomfort, and hassle of wearing it for a day is certainly less expensive than dying from a rifle shot, but the odds of ever encountering such a situation are so low it's not worthwhile.)

The last 6 mile diameter/civilization-destroying-sized thing was 65 million years ago. we won't be human in 65 million years, we could as well be animal or rodent by that time. Clearly we should spend $0 on the problem. As for city-destroying-sized things, odds are any will just land in uninhabited area. If a city does get hit, well, sucks to be them.

I suspect you like watching things blow up, but that's not really the wisest choice here. Much better would be an impactor with very high mass - perhaps a depleted uranium core - and low relative velocity: slow enough to contact the asteroid without shattering it and massive enough to nudge its trajectory and keep nudging it for a while. Post-contact booster rockets might help further. It's not something you launch in the eleventh hour, though.

Touching/Landing on asteroids is difficult because they have very complicated structures and rotations. The best way to deflect an asteroid is not by nukes or what you suggest, but by spraying it white (solar radiation pressure) or parking a mass (e.g. 1t) with a ion drive next to it.

You used the word contact, and I mean "next to it" in the sense that they are not in contact (gravitational pull only). But I think we just need to try it on some test asteroid -- e.g. to bring it into an orbit around the earth.

I do, but that's not the point. If it has any chance to cause global extinction due to its size, you can't make it explode with a nuke of a reasonable size. You can, however, nudge it with the explosion. Perhaps a contact explosion is not desirable, but you should still be able to press on an area of tens of thousands of square meters for a few seconds with a pressure sufficient to outmatch that heavy slow impactor. True, the lack of atmosphere doesn't help here, but perhaps some additional inert mass aroun

It doesn't just need to be a rocket, it needs to be a really big rocket. To deflect something potentially civilisation-destroying, you want to do it as early as possible. Inside lunar orbit is much too late. That means that you need to get a rocket out to it, and then match velocities (just ramming it won't be enough) and deliver the explosive to a sensible location. Ideally, you want to attach to the side and push it, rather than try to blow it up. We're talking something that would make the Apollo ro

Since the elite only need about 8% max of the population? lets face it the thing nobody wants to mention is for the first time in history technology has pretty much made most peasants completely worthless. With robots and automation you can have entire factories run by just a couple of low skilled button pushers and even in the tech sector you are seeing the rise of smart servers and other gear that simply tells some monkey when to replace a failing part so the billions of peasants you have now simply are n

not true, if you remember the Monty Python show "Is there Life After Death", with guests of several prestigious dead peope, there was un-aired segment of cost-benefit analysis questions asked of the dead, and it turns out dead people do not make convincing cost effectiveness arguments at all.

IANAA (Astrophysicist), but I believe asteroids of that size would reach the earth. Depending what it's made of, it could break into a lot of pieces, though.

This is a pretty small asteroid and (again, I'm no expert) but its orbit means that it wouldn't have a great relative velocity if it did strike earth (nothing like a comet, by comparison). There were some estimates on the damage it would do if it were to strike in the referenced article and this doesn't seem to be a major concern.

The Earth's atmosphere is equivalent to 10.3 meters of water in mass per area. Re-entry heating gets split between the meteorite and the air it is traveling through. When the meteorite mass per area is higher than the equivalent mass per area of the atmosphere, it tends to not pick up enough heat to melt entirely or drag to stop. Asteroid density va

There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns; the ones we don't know we don't know. - Donald Rumsfeld (Maybe meteors are what he was talking about?:)

I think you misunderstand the disaster that's coming. When the Mayan calendar ends, all computers that use the Mayan calendar will crash, world-wide. Worse yet, unlike Y2K, where we were able to drag old Cobol programmers out of retirement to fix the problem, experts in Mayan computers are all extinct. So we're all doomed! Except for those of us who don't use Mayan computers.:)

No, that isn't it. The disaster will be all the TV shows predicting disaster will go away, I love those. Worse, Giorgio Tsoukalos' hair will expand to the size of small planet and then catch on fire. It will be a holocaust of immense proportions. I'm looking forward to a gonzo-whopper of a End-O-the-Hair Moronic Convergence.

There have been around 514 leap years since it was created around 45 BC. Without the extra days every 4 years and all the adjustments that needed to be done to figure out leap years in the early days plus the Gregorian reform, today would be somewhere in the realm of July or August of 2013. So the 2012 thing should have happened several months ago.

The odds of any individual item hitting us are (pardon me) astoromically small. Even if it did have a "good chance" of hitting us, that would mean maybe 1% at this point. Obviosly rocks have hit earth before, and rocks will hit earth again, but I'm not going to lose any sleep over it.

TFA contains a link to an predicted impact table [nasa.gov] of DA14 with earth, going some 50 years into the future. The likelihood of each impact is rather small, and the cumulative probability of any impact is computed as 2.2e-04 (about 1 in 5000 - not alarming, but not exactly negligible IMO).

Here's what I don't understand: the first entry in the chart, corresponding to the next risk event, is in the year 2020. What happened to Feb 2013?

Mm, yes the reality is that our ability to discover and track these rocks is pretty limited. Our civilisation could be destroyed tomorrow and the first thing anyone would know about it would be when their clothes lit on fire.

Since we can predict the next (2013) close approach very accurately we're very confident it will be a miss. Therefore that approach doesn't rate a mention in the table.

The trouble comes in that, while we know the 2013 approach distance will be greater than 0km from the surface (>6400km from the centre) there's still some uncertainty. The earth is massive and the close approach will cause a relatively large change in the orbit of DA14. The size of the change is inversely proportional to the square of t

If it hit the ocean anywhere near land, it would still cause significant devastation. In "Lucifer's Hammer" by Larry Niven and Jerry Pournelle, a much larger object struck the Pacific Ocean - IIRC a mile in diameter. At 30,000 MPH relative, about 8.3 miles per second, that large object went through the depth of the Pacific in something less than one second, vaporizing cubic miles of water and causing a tsunami a couple thousand feet high, striking LA and washing over the mountains into the Central Valley.

Oh no! A 45 meter space rock might hit us, and it might mean the end of the world, even though we're about 26,000 mi in diameter and it will probably burn up in the atmosphere! And of course, we all know when someone throws a pebble at a person, that person EXPLODES! WE ARE ALL DOOM-ED!

Looks like someone skipped class that day the high school physics teacher went over kinetic energy.

NASA places the odds at 99.9988% chance of a miss. That is almost, but not quite, 5-nines. With all the downtime I've seen from companies promising 5-nines of reliability and failing, I'm more than a little skeptical.

The number of asteroids passing close to the Earth has not changed recently, but the number we know about has increased dramatically. The current statistics are around 8700 known NEO's, which is double what we knew about 5.5 years ago, 4 times that of 9.5 years ago, and 10 times that of 12.5 years ago. Therefore the number of *known* close passes will continue to go up.

In the silver lining department, the more NEO's we know about, the more chances for space mining, and the better chance we have of prevent

45m would be roughly comparable to Tunguska. It could completely fuck up a large metropolitan area, but only with a direct hit on land. Otherwise all you get is a sizeable earthquake and possibly a tsunami, which sucks, but is nothing we haven't seen several times in the last decade.

The point is that it would be a big explosion, but even at its most devastating it wouldn't come close to an extinction event.

If it hit the ocean the equivalent volume of water would be displaced, and quite a bit of it would be vaporized. So I would argue that the result would be a significant tsunami (bigger than Japan? I don't know) and a change in the weather for a year or two.

Not even close. It wouldn't change the weather at all on the scale of days. The energy needed for a tsunami like the one that hit Japan just short of a year ago requires enormous amounts of energy. The thing is that the earth is really really big, and even though this rock is moving pretty fast, its not that fast, and its not that big. It is comparable to nuclear weapons that have been tested, these did not change weather or produce "significant" tsunami's. At lest not at the scale you are thinking of.

Someone in an earlier comment pointed out that the Barringer Crater was thought to have been made by a rock about 55 meters in diameter. I was extrapolating from that. That crater is substantially bigger than anything humans have managed including fusion bombs. But It's an arguable point, especially since I'm too lazy to do any of the math.:)

Fusion bombs have (almost) all been air-bursts or fully contained underground tests, and for good reason: the 100-kiloton Sedan [wikipedia.org] nuclear excavation test of Operation Plowshare [wikipedia.org] was responsible for 7% of all radioactive contamination from US nuclear testing.

I just saw a picture of the concrete dome built over a Cactus Crater [artificialowl.net] recently ( this is a different picture). That dome is 107m (390 feet) in diameter. The Castle Bravo test left a crater over a mile (2000 meters) in diameter and 250 feet (75 meters) deep. I also found this article [rense.com] that notes that some of the nuclear tests caused tsunamis hundreds of miles away on Christmas and Pitcairn islands. Some of those tests were as 'small' as 16 kilotons. But a 1996 analysis said that tsunamis from underwater

The risk, for this asteroid as has been pointed out before is negligible. Anyone who follows http://www.spaceweather.com/ knows 2 or 3 times a year some small piece of rock comes between the earth and moon. Furthermore a few 10 MT nukes can easily either vaporize or at the very least break up into many small pieced a 150 foot chunk of rock. The technology to deliver such a device millions of miles out has been already proven by the recent asteroid and comet intercept probes. A single MIRV, attached to

...I was wrong when I once said that all the crazy people should be let out of the hospitals and let to run the governments of the US. Nope, it is now very clear that the crazy people should be kept locked up, and furthermore should not be allowed to read the news or anything above their education levels.
I mean...I really think that "Interpretation 101" should be elected as a required course, starting in elementary school. Because it is again, very clear, that people should not be allowed to interpret any

Watching the movie Armageddon does NOT make you a fucking expert in the subject of Near-Earth Asteroids. Like the newer article on the site has indicated, you know nothing about the subject and are incapable of even recognizing those who do.

on the premise that we have accurately predicted a large asteroid impact on Earth in a decade from now. Film follows the effect this has on people all over the world, from the time of the announcement to the impact itself. From those who don't believe, to those who look forward to it or see it as the holy Armageddon they've been waiting for. The scary thing is many Christians do look forward to that!

Are you kidding me? The MOON is almost 400,000 km away. A massive, dangerous object passing within 3,000 km isn't "close"? To a planet that's 13,000 km in diameter? This asteroid will be within SPITTING distance of Earth.